I know you've had a ton of ideas thrown at you in this thread, but I've been thinking about your site since donating and I think what would be really amazing, if you can accomplish it somehow, is a way to encourage people to donate regularly.
There are probably many ways you could do this, but here's one: allow people to donate a sum of money, up front, that is not assigned to a particular person who needs treatment. Periodically prompt this person to fund treatments using some portion of this sum. Alternatively, support subscription billing where each time the money is withdrawn, the person is notified and asked to assign the money that was withdrawn to a particular person who needs it.
I really feel that a recurring process of some kind could both vastly increase the amount of money you raise, and also benefit donors by giving them a periodic uplift in their mood and level of happiness. It could become, if this word is not too misplaced, addictive.